The long-term goal of the research is to understand the neural mechanisms of limb position sense and cutaneous tactile sensibility and how cutaneous sensory neurons trophically influence the skin and its sensory receptor organs. The emphasis in this grant is on limb position sense because recent findings have suggested that muscle rather than articular receptors measure joint angle. Consistent with this idea, spinal tract neurons that signal joint angle (for the hindlimb, these lie in the dorsal part of the lateral fasciculus and not, as commonly believed, in the dorsal columns) have been found to be activated primarily by muscle receptors. We propose to continue the analysis of the spinal pathway in the cat and extend the study to the thalamus and cerebral cortex to characterize the response properties of the position signaling neurons and identify the sensory receptors that excite them.